1. Field of the Invention
The present invention relates to a simulated marble article. In particular, it relates to a simulated marble article having a high resistance to abrasion and a high transparency.
2. Description of the Related Art
Heretofore, simulated marble articles of resin concrete comprising a resin matrix of, e.g., polyester or acrylic resin, and a filler of, e.g., calcium carbonate, calcium sulfate, clay, silica, calcium silicate, and alumina trihydrate, are known (see: U.S. Pat. Nos. 3,405,088 and 3,847,865). Such simulated marble articles are used as building products, kitchen and bathroom counter tops, table plates, dresser tops, vanity tops, shelving, wainscoting, and baths, among others.
Generally, simulated marble articles of resin concrete are produced by adding a prepolymer with a polymerization initiator, a filler and other additives, mixing these ingredients, and effecting vacuum degassing to obtain a mixture in the form of a slurry. The filler has a particle size of between several micrometers and 0.5 millimeter. The mixture in the form of a slurry is poured into a mold and allowed to stand at a room temperature or heated at a raised temperature to cure the slurry. The resultant shaped article is then subjected to cutting, bending by heat, lamination, surface finishing, etc. to obtain the above-mentioned kitchen and bathroom counter tops, table plates, dresser tops, baths, etc.
In the prior art, resin concretes comprise, as a filler, an inorganic powder having a relatively large particle size of several micrometers to 0.5 millimeter and, therefore, adhesion between the filler and a resin matrix is weak, resulting in the filler becoming detached by scratching, abrasion, etc. To eliminate this defect, a hard coating or a gel coating is formed on the surface of a resin concrete, which complicates the production process and thereby increases the cost.
Hard coating of the article, for improving the resistance to abrasion, is carried out by optionally first precoating the surface of a resin concrete body with a primer; then coating that surface with a solvent-diluted hard coating agent such as an organosilane hard coating agent and polyfunctional acrylic hard coating agent; drying the article to remove the solvent from the coating; and curing the resultant article by heating, or ultraviolet (UV) radiation etc. The above hard coating process has a problem in that it involves several processing steps. Further, control of the temperature and humidity after coating a hard coating agent on the surface of a resin concrete body is difficult since the solvent must be gradually removed from the coated layer to ensure that cracks do not appear, and thus entails the need to use large-scale air conditioning equipment. Moreover, the characteristics of hard coating agents limit the thickness of the hard coating layer to an extremely thin thickness of from 3 to 8 .mu.m, resulting in insufficient hardness and strength of the coating layer. Further, the adhesion between the substrate of the resin. concrete body and the hard coating layer is insufficient except for a limited combination thereof, and thus it is likely that the coating layer will be easily peeled from the substrate.
Another way to improve resistance to abrasion is gel coating, which is generally carried out for aesthetic and protective purposes on shaped articles of resin concrete, fiber reinforced plastics, etc. For example, in the above process, isophthalic acid series are used for polyester resins. In this process, a resin layer which does not contain glass fibers but may contain a filler such as calcium carbonate, silica etc. is formed on the surface of a mold and, after gelation occurs, a lamination process is carried out to produce a shaped article with a gel coating layer. A shaped article with a gel coating layer has excellent resistance to water, resistance to chemicals, and a high mechanical strength.
However, the lamination process must be carried out after the gelation of a gel coating layer, making the shaping process complicated. In particular, it is difficult to provide a molded article with a gel coating layer by a single shaping process and layer-peeling is likely to occur due to insufficient adhesion.
Furthermore, it is desirable to establish a high transparency of a resin concrete to give, to a simulated marble article, an appearance of high quality, preferably while allowing various resin materials and additives to be used in order to obtain the desired properties of a resin matrix or a simulated marble article for various applications.